Reflector which exhibits good reflectance over wide angle range and liquid crystal display using the same

ABSTRACT

Light-reflective concave portions are disposed on the surface of a substrate. The concave portions have a first and second vertical section perpendicular to each other. The first vertical section has an internal shape defined by a first curve and a second curve, the first curve extending from one point on the peripheral edge of the concave portion to the deepest point of the concave portion, and the second curve extending continuously from the first curve and from the deepest point of the concave portion to another point on the peripheral edge of the concave portion. The average of the absolute value of an inclination angle of the first curve is larger than that of the second curve relative to the substrate surface. The second vertical section has an internal shape defined by a shallow curve and deep curves formed at both sides of the shallow curve.

This application is a divisional application of U.S. application Ser.No. 10/180,434 filed on Jun. 26, 2002, now U.S. Pat. No. 6,695,454entitled “Reflector Providing Particularly High Reflectance in anIntended Viewing Angle and Reflection Type Liquid Crystal Display DeviceUsing the Same”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to reflectors which are suitable for usein liquid crystal displays using external light, a front light, abacklight, etc., as a light source, and to liquid crystal displays usingthe reflectors. More specifically, the present invention relates to areflector which exhibits good reflectance over a wide angle range andespecially high reflectance in a reflection direction in a desiredrange, and to a liquid crystal display which uses the reflector so thatit has a wide viewing angle and exhibits moderate directionality suchthat the display appears sufficiently bright when seen from a typicalviewing area.

2. Description of the Related Art

Liquid crystal displays are commonly used as display units for mobilecomputers, etc., and reflective liquid crystal displays, which useexternal light as a light source, are one kind of liquid crystaldisplays which are commonly used because of their low power consumption.In addition, liquid crystal displays having a front light for obtainingextra light in addition to external light are also commonly used.

In such liquid crystal displays, external light incident on the displaysurface (from the observer side) or light emitted from a front light isreflected by a reflector and is emitted outside the display surface, sothat a user can view an image which changes in accordance with thealignments of liquid crystal molecules in a liquid crystal layer.

In addition, liquid crystal displays having a backlight for obtainingextra light in addition to external light are also commonly used. Inliquid crystal displays having a backlight, a semi-transmissivereflector is used in order to reflect external light and to pass lightemitted from the backlight.

The inventors have performed various investigations with respect to therelationship between the shape of the surface of a reflector (the shapeof the surface closer to a display surface) and reflectioncharacteristics of the reflector.

When a reflector having a flat, specular surface is used, the reflectorexhibits extremely high reflectance at a specific reflection angledetermined in accordance with an incidence angle. However, areflection-angle range in which high reflectance is obtained isextremely narrow. Thus, a reflector having high directionality such thata viewing area from which the reflector appears bright is narrow isobtained. In addition, visibility is degraded due to so-called backreflection, that is, reflection of a light source, an observer's face,etc. in a display surface.

Accordingly, several techniques have been suggested in which concaveportions having shapes like parts of a sphere, grooves, or irregularconcavities and convexities are formed over the surface of a reflectorin order to obtain good reflectance over a wide range. According tothese techniques, reflection characteristics can be made such that thereflector appears bright over a wide viewing area.

FIG. 9 shows a reflector in which a plurality of concave portions eachshaped like a part of a sphere are formed on the surface of thereflector. With reference to FIG. 9, a reflector 51 is constructed byforming a plate-shaped resin base member 53 (a base member of thereflector) made of a photosensitive resin layer, etc., on a substrate 52made of glass, etc., and forming a plurality of concave portions 54 overthe surface of the resin base member 53. The inner surfaces of theconcave portions 54 are shaped like a part of a sphere, and the concaveportions 54 are formed continuously so that the concave portions 54overlap one another. In addition, a reflective film 55 formed of a thinlayer of aluminum, silver, etc. is formed on the concave portions 54 byvapor deposition, plating, etc.

The concave portions 54 are formed such that the depth thereof varies inthe range of 0.1 μm to 3 μm, and are irregularly arranged such that thepitch between the concave portions 54 varies in the range of 5 to 50 μm.In addition, the inner surface of each concave portion 54 is shaped likea part of a single sphere, and an inclination angle thereof is set inthe range of −18° to +18°.

The term “depth of a concave portion” used herein means the distancebetween the substrate surface of a reflector and the deepest point of aconcave portion, and the term “pitch between adjacent concave portions”used herein means the distance between the central points of adjacentconcave portions, which have a circular shape as seen in a plan view. Asurface as used herein is essentially a flat surface that disregards theminute irregularities (e.g. relatively microscopic crevasses orprojections) present in almost every physical layer. Such a flat surfaceincludes, for example, the substrate surface in which the concaveportions are non-existent or are completely filled in.

In addition, “inclination angle” means an angle of a tangential line atan arbitrary point on the inner surface of the concave portions 54relative to the substrate surface in a specific vertical section.

The reflector 51 has reflection characteristics similar to those of acomparative example (see FIG. 6), which will be described below. FIG. 6is a graph showing the reflection characteristics in the case in whichan incidence angle is 30°, where the vertical axis shows reflectance(reflection intensity) and the horizontal axis shows a reflection angle.

With reference to FIG. 10, an incidence angle is defined as an angle ω₀between the normal H of the reflector 51 (substrate surface) andincident light J. In addition, a reflection angle is defined as an angleω between the normal H and reflection light K on a plane including thenormal H and the incident light J. In addition, a specular reflectionangle relative to the substrate surface is defined as an angle at whichthe incidence angle ω₀ and the reflection angle ω are the same.

As shown in FIG. 6, for a specular reflection angle of 30°, thereflector 51 has a relatively good reflectance in the range of15°≦ω≦45°.

The above-described reflector 51 of the known art exhibits relativelygood reflectance over a relatively wide angle range due to the concaveportions. However, as shown FIG. 6, reflectance at 30°, which is thespecular reflection angle, is relatively low compared with two peaks at15° and 45°. Accordingly, reflection characteristics of the reflector 51are such that although relatively good reflectance is ensured for arelatively wide range, brightness is reduced in the specular reflectionangle.

However, when display units installed in devices such as notebookcomputers, desk calculators, watches, etc., are viewed, the direction ofa light source (incidence angle) and a viewing angle of a user whoreceives reflection light (reflection angle) are normally in a specificrange. Accordingly, it would be more convenient for the user to providea display which not only appears bright in a wide area but also exhibitsespecially high reflection intensity in a specific direction.

In addition, in the case in which the above-described reflector, whichappears bright over a wide viewing area, is used in liquid crystaldisplays having a backlight, a problem exists in that light emitted fromthe backlight is diffused too widely at the surface of the reflector andlight emitted in the specular reflection angle, which is the angle atwhich a user normally views the display, is reduced.

SUMMARY OF THE INVENTION

In order to solve the above-described problems, an object of the presentinvention is to provide a reflector which exhibits good reflectance overa wide angle range and especially high reflectance in a reflectiondirection in a desired range, especially in a direction shifted from adirection of specular reflection, and which prevents light emitted froma backlight from being diffused too widely. In addition, it is also anobject of the present invention to provide a reflective liquid crystaldisplay which uses the reflector so that it appears bright over a wideviewing area and exhibits moderate directionality in a normal viewingarea.

In order to solve the above-described problems, the present inventionprovides a reflector including a substrate having a plurality oflight-reflective concave portions on the surface thereof, each concaveportion having a first vertical section and a second vertical sectionwhich pass through a deepest point of the concave portion.

The first vertical section has an internal shape defined by a firstcurve and a second curve, the first curve extending from one point onthe peripheral edge of the concave portion to the deepest point of theconcave portion and the second curve extending continuously from thefirst curve from the deepest point of the concave portion to anotherpoint on the peripheral edge of the concave portion, and the average ofthe absolute value of an inclination angle of the first curve relativeto the substrate surface is larger than the average of the absolutevalue of an inclination angle of the second curve relative to thesubstrate surface.

The second vertical section is perpendicular to the first verticalsection and has an internal shape defined by a shallow curve and deepcurves formed at both sides of the shallow curve, the deep curves havinga smaller radius of curvature compared with the shallow curve.

Although the direction of the first vertical section is not determined,the vertical section along the up-down direction or the front-backdirection relative to an observer is preferably defined as the firstvertical direction.

As described above, in the reflector of the present invention, aplurality of light-reflective concave portions are formed on thesubstrate surface, and each of the concave portions has a curved surface(concave surface). Accordingly, the reflector appears bright from a wideviewing area and has a light-diffusing characteristic so that backreflection is suppressed.

The internal shape of each concave portion along the first verticalsection is defined by the first curve and the second curve which areconnected to each other at the deepest point. The first and the secondcurves are formed such that the average of the absolute value of theinclination angle of the first curve relative to the substrate surfaceis larger than the average of the absolute value of the inclinationangle of the second curve relative to the substrate surface. Morespecifically, the inclination of the first curve is relatively steep andthe inclination of the second curve is relatively gentle, and the secondcurve is longer than the first curve.

Accordingly, the amount of light reflected by the surface at regionsaround the second curve is larger than the amount of light reflected bythe surface at regions around the first curve. More specifically,luminous flux density of reflection light in the direction of specularreflection relative to the surface at regions around the second curve isincreased. Accordingly, when the first curves in each concave portionare aligned in a specific direction (or in a plurality of specificdirections), reflectance in the specific direction(s) can be increasedover the entire region of the reflector.

In addition, internal shape of each concave portion along the secondvertical section, which is perpendicular to the first vertical section,is defined by the shallow curve and the deep curves formed at both sidesof the shallow curve, the deep curves having a small radius ofcurvature. Accordingly, reflectance in the direction of specularreflection can be increased. Preferably, the deep curves are formedsymmetrically across the shallow curve.

As a result, the overall reflection characteristics in the firstvertical section are made such that peak reflectance is obtained atabout the specular reflection angle and reflectance in the direction inwhich light is reflected by the surface at regions around the secondcurve B is increased. More specifically, reflection characteristics inwhich reflection light is moderately condensed in a specific directionwithout reducing the intensity of reflection light in the direction ofspecular reflection can be obtained.

According to the present invention, the concave portions are preferablyformed such that the first vertical sections and the second verticalsections of each concave portion are aligned in the same direction andthe orientations of the first curves in each concave portion are thesame. More specifically, the orientations of the first curves in eachconcave portion are preferably made the same, and the orientations ofthe second curves in each concave portion are also preferably made thesame.

In such a case, reflectance in the direction in which light is reflectedby the surface at regions around the second curve B is increased overthe entire region of the reflector. Accordingly, reflectioncharacteristics in which reflection light is moderately condensed in aspecific direction can be obtained.

In addition, according to the present invention, the inclination angleof the first curve relative to the substrate surface and the inclinationangle of the second curve relative to the substrate surface arepreferably substantially zero at the point at which the first curve andthe second curve are connected to each other. In addition, preferably,when the inclination angle of the first curve is negative and theinclination angle of the second curve is positive, the inclination angleof the first curve is gradually increased from a negative value and theinclination angle of the second curve is gradually reduced from apositive value, and both the inclination angles of the first and secondcurves become substantially zero at the point at which the first andsecond curves are connected to each other.

Accordingly, the internal surfaces of each concave portion can be madesmooth over the entire regions thereof, and reflectance in the directionof specular reflection can be prevented from being reduced.

Preferably, the concave portions are irregularly formed such that thedepth thereof varies in the range of about 0.1 μm to 3 μm.

When the depths of the concave portions are less than about 0.1 μm,sufficient light-diffusing effect cannot be obtained. When the depths ofthe concave portions exceed about 3 μm, the thickness of the substrate,which must be larger than the depths of the concave portions, becomestoo large and leads to problems in the manufacturing process anddeterioration in product quality. Further, because a moiré patternoccursdue to light interference when the concave portions are formedregularly, by forming the concave portions with various depths theemergence of a moire pattern is avoided. In addition, the reflectionlight is prevented from converging too sharply at a predeterminedviewing angle and the amount of reflection light varies smoothly in theviewing area.

Preferably, the concave portions are irregularly arranged next to eachother.

When the concave portions are formed separately, regions at whichspecular reflection occurs are increased since the regions between theconcave portions are flat, and sufficient light-diffusing effect cannotbe obtained in the limited pixel area. Accordingly, the concave portionsare preferably formed next to each other. In addition, the concaveportions are preferably formed irregularly since the moiré patternappears when the concave portions are formed regularly.

The present invention also provides a reflective liquid crystal displaywhich includes one of the above-described reflectors. Preferably, theconcave portions are formed such that the first vertical sections andthe second vertical sections of each concave portion are aligned in thesame direction and the orientations of the first curves in each concaveportion are the same, and the reflector is installed such that the firstcurves are disposed above the second curves in each concave portion whenviewed by an observer.

When the first curves are disposed above the second curves in eachconcave portion when viewed by the observer, external light, which ismainly incident from the upper side, can be reflected in a directionshifted toward the normal of the substrate surface from the lower sideof the observer.

In addition, since external light, which is mainly incident from theupper side of the observer, is efficiently received at regions aroundthe second curves, the amount of reflection light is increased over theentire region.

In addition, the amount of light reflected in the direction of specularreflection can be increased due to the reflection at the shallow curvein the second vertical section.

Accordingly, the amount of light reflected toward the eyes of theobserver is increased, and a reflective liquid crystal display whichappears bright from the viewpoint of the observer can be obtained.

The present invention also provides a reflector in which peakreflectance is obtained at about the specular reflection angle and anintegrated value of reflectance in a reflection-angle range smaller thana specular reflection angle with respect to the substrate surface isdifferent from an integrated value of reflectance in a reflection-anglerange larger than the specular reflection angle.

Accordingly, when a normal viewing angle of the observer is displacedfrom the direction of specular reflection relative to the substratesurface, a reflector in which light is mainly reflected in the directionof the normal viewing angle without reducing the amount of reflectionlight in the direction of specular reflection can be obtained.

The present invention also provides a reflective liquid crystal displaywhich includes a reflector in which peak reflectance is obtained atabout a specular reflection angle and an integrated value of reflectancein a reflection-angle range smaller than a specular reflection anglewith respect to the substrate surface is different from an integratedvalue of reflectance in a reflection-angle range larger than thespecular reflection angle. The reflector is installed such that thereflection-angle range corresponding to the larger of the integratedvalues of reflectance is disposed at the upper side of the specularreflection angle with respect to the substrate surface when viewed by anobserver.

According to the present invention, external light, which is mainlyincident from the upper side, can be reflected in the direction shiftedtoward the normal of the substrate surface from the lower side of theobserver.

Accordingly, when the reflective liquid crystal display of the presentinvention is used as a display for a mobile phone or a notebookcomputer, the amount of light reflected toward the eyes of the observeris increased, and a reflective liquid crystal display which appearsbright from the viewpoint of the observer can be obtained.

As described above, according to the present invention, a reflector canbe obtained which has a light-diffusing characteristic so that incidentlight is diffusely reflected and back reflection is suppressed over awide viewing angle, and in which the amount of reflection light in theviewing-angle range in which the observer normally views the display isincreased.

In addition, in a reflective liquid crystal display containing thereflector of the present invention, display surface appears especiallybright when viewed in a specific viewing-angle range so that visibilityis improved, and back reflection is suppressed over a wide viewing-anglerange.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a reflector according to an embodimentof the present invention;

FIG. 2 is a perspective view of a concave portion according to theembodiment;

FIG. 3 is a sectional view of the concave portion along a first verticalsection;

FIG. 4 is a sectional view of the concave portion along a secondvertical section;

FIG. 5 is a diagram showing the reflection characteristics of areflector according to the embodiment;

FIG. 6 is a graph showing the relationship between a light-receivingangle and reflectance;

FIG. 7 is a sectional view showing the layer structure of the reflectiveliquid crystal display according to the embodiment;

FIG. 8 is a diagram showing a manner in which the reflective liquidcrystal display according to the embodiment is used;

FIG. 9 is a perspective view showing a reflector of the known art; and

FIG. 10 is a diagram showing an incidence angle and a reflection angle.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will be described below withreference to the accompanying drawings; however, it is not intended tolimit the scope of the present invention.

FIG. 1 is a diagram showing a reflector 1 according to an embodiment ofthe present invention. As shown in FIG. 1, the reflector 1 of thepresent embodiment is constructed of a plate-shaped substrate 2 formedof, for example, aluminum. A plurality of light-reflective concaveportions 3 a, 3 b, 3 c, . . . , (denoted as concave portions 3 when theyare generically described) are irregularly formed next to each other onthe surface S (standard surface) of the substrate 2.

The internal shape of the concave portion 3 is shown in FIGS. 2 to 4.FIG. 2 is a perspective view of the concave portion 3, FIG. 3 is asectional view of the concave portion 3 cut along a first verticalsection X, and FIG. 4 is a sectional view of the concave portion 3 cutalong a second vertical section Y, which is perpendicular to the firstvertical section X.

As shown in FIG. 3, the internal shape of the concave portion 3 alongthe first vertical section X is defined by a first curve A and a secondcurve B, the first curve A extending from one point S1 on the peripheraledge to the deepest point D, and the second curve B extendingcontinuously from the first curve A from the deepest point D to theother point S2 on the peripheral edge. With reference to FIG. 3, thefirst curve A extends downward toward the right, and the second curve Bextends upward toward the right. In addition, both an inclination angleof the first curve A relative to the substrate surface S and aninclination angle of the second curve B relative to the substratesurface S are substantially zero at the deepest point D, where the firstcurve A and the second curve B are smoothly connected to each other.

The inclination angle of the first curve A relative to the substratesurface S is steeper than the inclination angle of the second curve B,and the deepest point D is at a position shifted toward the x directionfrom the central point O of the concave portion 3 (i.e. the deepestpoint D and the central point O of the concave portion are notvertically aligned). More specifically, the average of the absolutevalue of the inclination angle of the first curve A relative to thesubstrate surface S is larger than the average of the absolute value ofthe inclination angle of the second curve B relative to the substratesurface S. The average of the absolute value of the inclination angle ofthe first curve A relative to the substrate surface S in the concaveportions 3 a, 3 b, 3 c, . . . , varies in the range of about 2° to 90°.In addition, the average of the absolute value of the inclination angleof the second curve B relative to the substrate surface S in the concaveportions 3 a, 3 b, 3 c, . . . , varies in the range of about 1° to 89°.

In addition, as shown in FIG. 4, the internal shape of the concaveportion 3 along the second vertical section Y is approximatelysymmetrical about the vertical line passing through the central point Oof the concave portion 3. The region around the deepest point D isdefined by an almost linear, shallow curve E having a large radius ofcurvature, and regions at the right and left sides of the shallow curveE are defined by deep curves F and G having a small radius of curvature.In each of the concave portions 3 a, 3 b, 3 c, . . . , the absolutevalue of an inclination angle of the shallow curve E relative to thesubstrate surface S is generally about 10° or less. In addition, theabsolute values of inclination angles of the deep curves F and Grelative to the substrate surface S in the concave portions 3 a, 3 b, 3c, . . . , vary in the range of, for example, about 2° to 90°. Note thatalthough the term “each of the concave portions” is used in multipleplaces throughout the detailed description, a substantial majority ofthe concave portions may be used as well as every concave portion. Aslong as the effects described herein are achieved, the absolutepercentage of concave portions which are, for example, oriented inexactly the same direction is inconsequential.

In addition, the distance between the deepest point D and the substratesurface S is defined as the depth of each concave portion 3, and thedepth of the concave portions 3 a, 3 b, 3 c, . . . , varies in the rangeof about 0.1 μm to 3 μm.

In the present embodiment, the first vertical sections X of each of theconcave portions 3 a, 3 b, 3 c, . . . , are aligned in the samedirection. Similarly, the second vertical sections Y of each of theconcave portions 3 a, 3 b, 3 c, . . . , are aligned in the samedirection. In addition, the orientations of the first curves A in eachof the concave portions 3 a, 3 b, 3 c, . . . , are the same. Morespecifically, in every concave portion, the x axis shown in FIGS. 2 and3 extends in the same direction.

In the reflector 1 of the present embodiment, the orientations of thefirst curves A in each of the concave portions 3 a, 3 b, 3 c, . . . ,are the same. Accordingly, as shown in FIG. 5, the reflectioncharacteristics of the reflector 1 are such that the reflectiondirection is shifted from the direction of specular reflection relativeto the substrate surface S.

More specifically, as shown in FIG. 5, the reflection light Kcorresponding to incident light J, which is incident at an angle fromthe upper side of the x direction, is shifted such that a viewing areafrom which the display appears bright is shifted from the direction ofspecular reflection K₀ toward the normal H relative to the substratesurface S. The angles formed by the incident light J and specularreflection K₀ are symmetric around the normal H of the substrate surfaceS.

In addition, as described above, the internal shape of each concaveportion 3 along the second vertical section Y, which is perpendicular tothe first vertical section X, is defined by the shallow curve E having alarge radius of curvature and the deep curves F and G having a smallradius of curvature. Accordingly, reflectance in the direction ofspecular reflection relative to the substrate surface can be increased.

As a result, as shown in FIG. 6, the overall reflection characteristicsin the first vertical section X are made such that peak reflectance isobtained at about the specular reflection angle and reflectance in thedirection in which light is reflected by the surface at regions aroundthe second curve B is increased. More specifically, reflectioncharacteristics in which reflection light is moderately condensed in aspecific direction without reducing the amount of reflection light inthe direction of specular reflection can be obtained.

More specifically, FIG. 6 shows the relationship between thelight-receiving angle (θ°) of a viewer and brightness (reflectance) inthe case in which external light is radiated onto the display surface ofthe reflector 1 of the present embodiment under a condition in which theincidence angle is 30°. The light-receiving angle is changed from 0°(angle corresponding to the normal) to 60° across the midpoint 30°,which is the specular reflection angle relative to the display surface(substrate surface). As a comparative example, the relationship betweenthe light-receiving angle and the reflectance in a reflective liquidcrystal display containing a known reflector having spherical concaveportions is also shown in FIG. 6.

As is apparent from FIG. 6, in the comparative example, the reflectanceis approximately constant when the light receiving angle is in the rangeof 15° to 45° (although there is somewhat of a decrease in emission atthe specular angle). In contrast, with respect to the reflector 1 of thepresent embodiment, peak reflectance is obtained at about 30°, that is,about the specular reflection angle relative to the substrate surface S.In addition, the integrated value of the reflectance in the range inwhich the light-receiving angle is smaller than the specular reflectionangle (30°) is larger than the integrated value of the reflectance inthe range in which the light-receiving is larger than the specularreflection angle. More specifically, sufficient brightness can beobtained at viewing angles around 20° while ensuring brightness in thedirection of specular reflection. The reason for this is that most userstypically view the display (for example, in computers, cellulartelephones, watches, PDAs) at angles of about normal to the surface toabout the specular reflection angle (or here a little larger—about 35°from normal), with angles around 20° being especially popular. Thus, theliquid crystal display should have increased brightness relative to aconventional liquid crystal display at least from about normal to thesurface to about the specular reflection angle.

Although the manufacturing method for the reflector 1 is not limited,the reflector 1 can be manufactured by, for example, the followingprocesses.

First, a punch (stamping tool) having a convex end portion correspondingto the shape of the above-described convex portions is prepared. Thepunch is held such that the end portion thereof opposes an aluminumsubstrate, and is repeatedly pressed against the aluminum substrate soas to form the convex portions over the entire area of a predeterminedregion of the aluminum substrate. While the punch is repeatedly pressedagainst the aluminum substrate, the orientation of the punch relative tothe aluminum substrate is maintained constant and the stroke andinterval are changed irregularly. The stroke is adjusted such that thedepth of the concave portion is in a predetermined range, and theinterval is adjusted such that a moiré pattern does not appear.

Of course, the reflector 1, is shown as formed from a single reflectivematerial. In another embodiment, the reflector 1 may comprise a baseportion onto which the concave portions were formed and a reflectivelayer disposed on the base layer. The base portion may be formed in amanner similar to that of the reflector 1, above, while the reflectivelayer may be formed by deposition, sputtering, evaporation or any othersuitable method. The base portion may be any material suitable forforming the concave portions, organic or inorganic (for example glass),while the reflective layer may be, for example, a thin metallic layer.Alternately, the base portion may be the substrate itself.

FIG. 7 is a sectional view showing the layer structure of a reflectiveliquid crystal display 100 containing the reflector 1 of the presentembodiment.

With reference to FIG. 7, in the reflective liquid crystal display 100,a display-side substrate 20 and a reflector-side substrate 10 opposeeach other with a liquid crystal layer 30 therebetween. The display-sidesubstrate 20 is transmissive and the reflector-side substrate 10 isreflective. The external surface of the display-side substrate 20 servesas a display surface, and the reflector-side substrate 10 is providedwith the reflector 1.

The reflector-side substrate 10 is formed by laminating a glasssubstrate 11, the reflector 1, a transparent intervening layer 13, acolor-filter layer 14, a transparent planarizing layer 15, a transparentelectrode layer 16 formed of an Indium Tin Oxide (ITO) film, a Nesafilm, etc., and an alignment layer 17, in that order from the bottom. Inaddition, the display-side substrate 20, which opposes thereflector-side substrate 10 across the liquid crystal layer 30, isformed by laminating an alignment layer 21, an insulating layer 22, atransparent electrode layer 23 formed of an ITO film, a Nesa film, etc.,a glass substrate 24, and a light-modulating layer 25 (a polarizingplate, a retardation plate, etc.) in that order from the liquid crystallayer 30.

Transparent electrodes of the transparent electrode layer 16 andtransparent electrodes of the transparent electrode layer 23 arearranged in striped patterns which perpendicularly cross each other, theliquid crystal layer 30 being disposed therebetween. Thus, asimple-matrix liquid crystal device is formed in which pixels are formedat intersections of the transparent electrodes of the transparentelectrode layer 16 and the transparent electrodes of the electrode layer23.

Of course, the transparent electrodes may be formed in other patternsand provided at different locations in the liquid crystal display 100,as can the color filters in the color-filter layer 14. For example, thecolor filters may be provided in the display-side substrate 20 ratherthan the reflector-side substrate 10, being formed on the substrate 24and having another insulating layer disposed the transparent electrodelayer 23 and the color filter for instance. Examples of possiblearrangements of the color filters include a stripe-type arrangementhaving different colors arranged successively side by side, a delta-typearrangement having colors arranged in a triangular shape, and amosaic-type arrangement having arranged successively side by side in avertical direction and a horizontal direction. In addition, the colorfilters may comprise different colors (red, blue, green, cyan, magenta,yellow or achromatic to name a few).

In the reflective liquid crystal display 100, the reflector 1 is alignedsuch that the first curves A in the concave portions 3 a, 3 b, 3 c, . .. , are placed in the x direction relative to the second curves B, whichhave gentler slopes. In addition, characters, etc., are displayed in theorientation such that the x direction is aligned with the upwarddirection.

FIG. 8 is a diagram showing the manner in which the reflective liquidcrystal display 100 is used. In FIG. 8, only the first curves A and thesecond curves B in the reflective liquid crystal display 100 are shownand other components are omitted for convenience.

The reflective liquid crystal display 100 is installed in a mobilephone, a notebook computer, personal data assistant, etc., in theorientation such that the x direction is aligned with the upwarddirection. In such a case, as shown in FIG. 8, the reflective liquidcrystal display 100 is normally set or held at an angle relative to thehorizontal plane such that the x direction is aligned with the upwarddirection. More specifically, when the reflective liquid crystal display100 is used, it is disposed such that the first curves A are above thesecond curves B in each concave portion when viewed by the observer. Inaddition, the observer normally looks down onto the reflective liquidcrystal display 100 from the upper side relative to the direction ofspecular reflection K₀ and from the lower side relative to thehorizontal plane.

In such a case, external light (incident light J), which is primarilyincident from the upper side, is mainly reflected by the surface atregions around the second curves B, so that reflection light K is noteasily directed toward the lower side of the observer but rather headsessentially toward the upper side relative to the direction of specularreflection K₀.

Accordingly, the viewing area from which the observer normally views thedisplay and the viewing area from which the display appears bright aremade the same. Therefore, a display which appears bright from theviewpoint of the observer can be obtained.

Although the reflective liquid crystal display according to the presentembodiment shown in FIG. 7 is constructed such that the reflector 1 andthe transparent electrode layer 16 are formed separately, thetransparent electrode layer 16 may also be formed of the reflector 1 andplaced at the position where the reflector 1 is formed in FIG. 7. Insuch a case, the transparent electrode layer also serves as a reflector,and the layer structure of the reflective liquid crystal display can bemade simpler.

In addition, the above-described reflector may be formed of asemi-transmissive, semi-reflective substrate such as a half mirror,etc., and an illumination plate may be disposed behind the liquidcrystal panel. In such a case, a semi-transmissive, semi-reflectiveliquid crystal display can be obtained which serves as a reflective typewhen external light is bright and serves as a transmissive type byilluminating the illumination substrate when external light is dark. Forthis, the liquid crystal display may also include a light sourcedisposed under or to one side of the display and additionally include alight guide to guide the light from the light source to at least thearea under the reflector and display. The present invention may also beapplied to such semi-transmissive, semi-reflective liquid crystaldisplays.

In addition, when a front light is disposed in front of the display-sidesubstrate 20, a front-light liquid crystal display can be obtained inwhich external light is exclusively used when the external light isbright and the front light is optionally used when the external light isdark. The present invention may also be applied to such front-lightliquid crystal displays.

The liquid-crystal driving method is not limited in the presentinvention, and the present invention may also be applied toactive-matrix liquid crystal displays using thin film transistors andthin film diodes, segmented liquid crystal displays, etc., in additionto the above-described simple-matrix liquid crystal display.

What is claimed is:
 1. A reflector comprising a substrate having aplurality of light-reflective concave portions on a surface thereof,each concave portion having a first vertical section and a secondvertical section which pass through a deepest point of the concaveportion, wherein the first vertical section has an internal shapedefined by a first curve and a second curve, the first curve extendingfrom a first point on a peripheral edge of the concave portion to thedeepest point of the concave portion, and the second curve extendingcontinuously from the first curve and from the deepest point of theconcave portion to a second point on the peripheral edge of the concaveportion, and a first average of an absolute value of an inclinationangle of the first curve relative to the substrate surface is largerthan a second average of an absolute value of an inclination angle ofthe second curve relative to the substrate surface, and wherein thesecond vertical section is perpendicular to the first vertical sectionand has an internal shape defined by a shallow curve and deep curvesformed at both sides of the shallow curve, the deep curves having asmaller radius of curvature compared with the shallow curve.
 2. Areflector according to claim 1, wherein the concave portions are formedsuch that the first vertical sections and the second vertical sectionsof each concave portion are aligned in the same direction andorientations of the first curves in each concave portion are the same.3. A reflector according to claim 1, wherein the inclination angle ofthe first curve relative to the substrate surface and the inclinationangle of the second curve relative to the substrate surface aresubstantially zero at the point at which the first curve and the secondcurve are connected to each other.
 4. A reflector according to claim 1,wherein the concave portions are irregularly formed such that the depththereof varies in a range of about 0.1 □m to 3 □m.
 5. A reflectoraccording to claim 1, wherein the concave portions are irregularlyarranged next to each other.
 6. A reflective liquid crystal displaycomprising a reflector according to claim
 1. 7. A liquid crystal displayaccording to claim 6, wherein the concave portions are formed such thatthe first vertical sections and the second vertical sections of eachconcave portion are aligned in the same direction and orientations ofthe first curves in each concave portion are the same, and the reflectoris installed such that the first curves are disposed above the secondcurves in each concave portion when viewed by an observer.
 8. Areflector according to claim 1, wherein the deep curves are formedsymmetrically across the shallow curve.
 9. A reflector according toclaim 1, wherein the deepest points and central points of the concaveportions are not vertically aligned.
 10. A reflector according to claim1, wherein the first average varies from about 2° to 90°.
 11. Areflector according to claim 1, wherein the second average varies fromabout 1° to 89°.
 12. A reflector according to claim 1, wherein anabsolute value of an inclination angle of the shallow curve relative tothe substrate surface is at most about 10°.
 13. A reflector according toclaim 1, wherein an absolute value of an inclination angle of the deepcurve relative to the substrate surface is about 2° to 90°.